Commey knocked out Alejandro Luna in the sixth round of a title elimination bout on Saturday night at Freeman Coliseum in San Antonio on the Mikey Garcia-Sergey Lipinets undercard. On Monday, his title fight was ordered.

The IBF sent 135-pound world titleholder Robert Easter Jr. a letter on Monday to formally notify him of his obligation to fight Commey in what would be a rematch.

In September 2016, Easter got knocked down by Commey in the eighth round but carried on and eked out a split decision to win a vacant world title, which he has gone on to defend three times, including by split decision against Javier Fortuna on Jan. 20.

The IBF letter to Easter congratulated him for retaining the belt against Fortuna and added, "We wish you all the best for a long and illustrious career as the IBF lightweight champion."

And then the mandatory was ordered.

"Your mandatory defense is due on or before March 30, 2018," the IBF wrote. "The leading available contender is No. 1 Richard Commey. ... Negotiations should start immediately and be concluded by April 12, 2018. If you are unable to reach an agreement by April 12, 2018, the IBF will call for a purse bid to determine who will promote the bout, when and where."

Easter (21-0, 14 KOs), 27, of Toledo, Ohio, was ringside in San Antonio to watch Commey's fight with Luna as well as Garcia's hard-fought unanimous decision against Sergey Lipinets in the main event.

Garcia's victory gave him a world title in a fourth weight division. He also currently holds a lightweight title and has 10 days to decide which belt to hang on to. Garcia said he is interested in one more fight at lightweight and wants a unification bout. Easter is hoping that he returns to lightweight to unify with him, which could lead to Easter asking for an exception to the mandatory against Commey in order to unify titles.

But Ghana's Commey (26-2, 23 KOs), fighting on his 31st birthday, will get a lightweight title fight sooner or later thanks to his victory over Luna (22-1, 15 KOs), 26, of Bellflower, California.

Commey knocked Luna down twice in the sixth round before referee David Fields waved it off at 1 minute, 54 seconds.

"He was exactly what I expected and if I had connected on more of my punches in the beginning I think the fight would have been over earlier," Commey said. "I was really trying to work on what we had been focusing on in camp but I just wasn't performing well at the start of the fight.

"It is the greatest feeling to get the win on my 31st birthday. I am looking forward to fighting for the 135-pound world title and becoming champion."